Project 1: Biochemistry The RecQ family of DNA helicases Includes the Werner syndrome (WS) protein WRN. Mutations in WRN are associated with genetic instability and age-related diseases, including an increase in specific cancers. Our long-term objective is to characterize the biochemical properties and functions of WRN, and to illuminate how they contribute to the maintenance of genomic integrity and avoidance of cancer. Our overall hypothesis is that WRN prevents collapse of replication forks by facilitating DNA synthesis past sites of covalent damage and by unwinding alternative secondary structures. We have the following Specific Aims: [1) To assess the role of WRN in facilitating replication of unrepaired DNA damage and alternate DNA structures by translesion ("errorprone") DNA polymerases and by DNA polymerase 8 (Pol 8), in collaboration with Project 2; [2] To delineate the interactions of WRN with telomerase and telomeric DNA,. in collaboration with Project 3 and Dr. Jack Griffith at the University of North Carolina;[3) To determine if reduction in WRN content results in a decrease in random mutations throughout the genome together with an increase in deletion mutations;. [4) To characterize the phenotypic manifestations of single nucleotide polymorphisms that[unreadable] greatly diminish WRN helicase activity, in collaboration with Core A and Dr. Gerardo Jimenez-Sanchez at the National Institute of Genomic Medicine, Mexico. These proposed studies, in concert with those in the other Projects and Cores, will contribute to our understanding of the roles of RecQ helicases in human biology and cancer.